I know of the mod adding the block animation when dual-wielding, but the block is actually done with a single weapon.
I've tried seraching on the Nexus but had no luck.
To rephrase: Is there an actual animation using 2 single-handed weapons to block?
I imagine the weapons being "crossed".
Best Answer
It depends on your definition...
The idle stance animation you see when dual-wielding (the one where you raise one hand in the air) is actually named the blocking stance for dual-wield in the game assets, but the blocking stance mechanic itself is never implemented in the finished product. I found out about it when making PCEA 1.0
So if you're asking "does the game actually has dual-wield block asset?" the answer is yes, it does, only repurposed
If you're asking "does the game has a dual-wield block asset that has never actually been used?" the answer is no, it doesn't
P.S: if you're wondering what the original dual-wield idle animation looks like, I don't know. I don't see anything named that in the game asset. If you're wondering where I found out about it, it's somewhere in the animation group data accessible through Creation Kit (I haven't touched it for about a year no and I don't have Skyrim installed)